Steering mechanism



Aug. 5, 1952 s. l. MaCDuFF STEERING MECHANISM Filed Nov. 18, 1948Patented Aug. 5, 1 952 STEERING MECHANISM Stanley I. MacDu', South Bend,Ind., assignor to Bendix Aviation Corporation, South Bend, Ind., acorporation of Delaware Application November 1s, 1948, serial No. 60,658'Y This invention relates to steering gear con- 6 Claims.. (Cl.180-79.2)

struction-and more particularly to novelmeans of piston construction foruse with power operated steering mechanisms.

It is a very important object of the invention to provide a novelconstruction for minimizing deleterious effects due to misalignment ofparts in a worm and nut steering gear of the hydraulic power actuatedtype.

A further object of the invention is to provide a novel construction ina hydraulic power steering mechanism of the concentric piston and ballnut type, wherein the nut may be adjusted laterallly1 relative to thepiston for preloading the ba s. 1

It is also an object of the invention to provide a single means ofadjustment in a hydraulic power steering mechanism of the concentricpiston and ball nut type for controlling the back-- lash of the gearsand for preloading the balls.

The above and other objects and features of the invention may beapparent from the following description taken in connection with theaccompanying drawing which forms a part of this specification and inwhich:

Figure 1 is a longitudinal sectional view of one form of steeringmechanism with which the invention is associated;

Figure 2 is a view in section taken on the lines 2--2 of Figure 1; and

Figure 3 is a top plan view of the central portion of the piston withparts broken away to show more clearly the manner of adjustablyassociating the worm and nut with the piston.

Referring now to Figurevl of the drawing, in which the invention isillustrated in connection with a steering mechanism, the referencenumeral I designates a housing or motor cylinder in which a piston I2 ispositioned for axial movement within the cylinder. The piston dividesthe cylinder into two opposed chambers I4 and I6. Movement of the pistonmay 'be accomplished through rotation of shaftk I8 which extendsthrough-the pistonrand housing and which is drivably connected to thepiston through a plurality of balls 20. The rotative action of the shaftis translated into an axial force on the nut to thereby move the pistonto the right or left depending upon the direction of rotation of theshaft. This piston movement is augmented by liiuid under pressure from asource, not shown,

acting in one or the other of chambers I4 and I5 when the resistanceoffered to turning thegshaft I8 exceeds a predetermined value determinedby the strength of a spring 22. .The spring normally holds an opencenter valve 24 in the position shown to thereby admit fluid pressuresimultaneously to the chambers I4 and I6 through the passages 26 and 28respectively. Since the effective areas of the ends of the pistonexposed to uid pressure are the same there is no movement of thepistonat this time when equal pressures are acting on its ends. Thevalve is equipped with inlet and outlet passages 3Il and 32communicating with the interior of the valve.

Y Deiiection of the spring 22, when the resistance offered to steeringVexceeds a predetermined value, permits a-valve spool 34 to move axiallyrelative to body member 36, so that one of the passages 26 and 28 isrestricted to inlet pressure and opened wider to exhaust pressure, andthe other of the passages is restricted to exhaust pressure and openedwider to inlet pressure. this function of the valve of the steeringmechanism forms no part of the invention a further discussion of theoperation of the valve is believed unnecessary. A more detaileddiscussion of the operation of an open center type valve can be found inPatent No. 1,790,620.

The piston I2, which is `arranged concentrically of the shaft, isprovided with enlarged end sections 40 and 42 anda reduced intermediatesection 44. The intermediate section is constructed with a rectangularslot 46 therein for receiving a rectangular nut member 48, which slideslaterally or floats in the slot. The nut abuts the ends of the slot, asbest shown in Figures 1 and 3, thus restricting axial movement of thenut. The enlarged ends of the piston are provided with bushings 45forming radial and axially slidable bearings for the shaft I8. The nutmember 48 is formed with interior helical grooves l5I) for receiving theballs 20 which also roll in mating helical grooves 52 of the rotatableshaft to thereby drivably connect the nut to said shaft. The shaft I8 isequipped with a longitudinal bore 54 in order to equalize the pressureacting on the ends of the shaft. This longitudinal bore communicateswith the exhaust port 32 through radial passage 56 of the shaft andpassage 58 in the valve body. The longitudinal bore also communicateswith the space between the piston ends through another radial passage59. A passage 60 in the valve body communicates the right side of thevalve 24 to the exhaust port. With this arrangement there is providedboth a balanced valve anda balanced shaft since both are as,aforementioned, in communication with the exhaust port at their ends.

The motor cylinder is furnished with end covf Since i ers 62 and 64 inwhich seal bushings Si' and 63 respectively are disposed for lateraldisplacement. These bushings 66 and 68 are bored at 'HJ and 'l2respectively to receive the shaft i8 which iits snugly in the bores tominimize leakage of fluid from chambers I4 and I6. The bushings are heldin position by snap rings 14 which fit into grooves in the endfcove'rs'so. that a portion ofthe Lsnap rings press against flanges 76 and 'i8 ofthebushings 66 and 68 respectively. These ilanges ride or float onelastic seal rings Si) carried in grooves 82 and 84 of the end covers tothereby-provide seals between the end covers and seal bushings.

It will be noted that there is" a radialspace between the bushings andtheend covers vto "allow for radial or lateral movement of the bushingsto compensate for eccentricities ofthe coaxially arranged parts such asthe piston and bearings. This arrangement also allows for lateraldistortion of the shaft I8.

` To return the balls from one'end ofV the nut to the other after 'theballs-havepassedout 'of the groovesv in the nut a transfer tube;iiisfprovided. This type of anti-friction screwfthreadis familiar tothose skilledin the'art andn'eedfnotV be discussed further'excepttopoint out that unless the balls are made the Iexact size 'of thegrooves, which is undesirable because 'this tends to vin'- crease thefriction ofthenut, there'will be considerable clattercaused byendplay'between the worm and nut. To eliminate this end play the ballsare preloaded radially.. In the present embodiment of the invention theballs are preloaded by laterally shifting the nut in the piston.

The nut 4s is dni/ably connected to a fsckshaft 8S through the'mediurnof a racl'fv inte.- gral With the nut, anda gear sector securelyxed to the rock'shaft and arranged in meshing relationshipfvvith therack. The vteetl'i'of the sector are generated .to'provide an axiallytapering tooth sector.

The aforementioned preloading .of f the balls may be accomplishedbyfaxial adjustment of the rockshaft, as best shovvn inFig'ure 2, whichmovement of the latter fshaft takes. 4up backlaslfi and` creates apressure' Orseparating force `between the intermeshing ``gear sector andrack. This pressure is transmitted through the balls to the shaft andfrornthe 'shaft through the 'bearings l5 to the piston "2. The piston,in turn, transmits this load to the cylinder Wall'. VA dual adjustmentis thus obtained through the arial shifting of the rockshaft. Anysuitable adjusting device for vthe rockshaft may be employed, such forexample asfthe one shown, Whichcomprises a stub shaft 94 having a swivelendv connection' 55 vwith the rockshaft `and a-threaded end portion 96threadedly' engaging a; cover plate El adapted to fit over an opening16% in thecylinder.

Although this invention has been described in connection lwith certain`speciiic embodiments, the principles are susceptible (3f-.numerousother applications that will readily occur to persons skilled in theart. Y

Having thus described the -various features of the invention, what Iclam asv new and desire to secure by Letters Patent is l. In a vmanuallyoperated-steering gearinechanisrn off the type utilizing hydraulic power.to assist steering, the combination of a motor cylinder with a pistontherein, bearings ,mounted in the ends of the piston,a; rotatableshaftextending through-the `cylinder andvpisto'n and 'carried by saidbearings, ,'said-pistonbeing arranged concentrically of the.slaft` for'axialmovement therealong, a nut carried by said shaft, mating' whichsaidnut abuts.

helical grooves in the nut and on a portion of said shaft, and aplurality of balls in said helical grooves for drivably connecting thenut to said shaft to thereby move said nut axially in response torotation of the shaft, said piston having a lateral opening forreceiving said nut, said lateral opening having sides forming shouldersagainst 2; Ina manually operated steering gear mechanism of the Vtypeutilizing hydraulic power to assist steering, the combination of a motorcylinder -rwith a piston therein, a bearing in each end of the piston, arotatable shaft extending through the cylinderand carried in thebearings, saidi'fpiston being arranged concentrically of the shaft:for'aXial-'movement therealong, a nut carried by saidshaft, matinghelical grooves in the nut and on a portion of said shaft, and aplurality of balls in said helical grooves for drivably connecting thenut to said shaft to thereby move said nutl axially in response torotation of said shaft, said piston having a lateral opening forlreceiving said nut, said-lateral opening having sides forming lshouldersagainst Which saidnut abuts,.and adjustable means for Ycausing relativelateral movementbetween said nut and piston forpreio'ading the balls.

3; -ln a manually operated steering gear mechanism of the type utilizinghydraulic power to assisvsteering, the combinationof ,a motor cylinderwith a pistenftherein having: a slot located intermediate Vitseriola-arotatable shaft in the motor cylinder, said piston arrangedconcentrically on said shaft for axial movement therealong, a nutconcentric with said shaft and positioned in saidslot for lateralmovement relative to said piston, said nut and ay portion of said shaft'having `mating lhelical grooves therein, a plurality of balls in saidgrooves arranged for .drivably yconnecting'the vnut tosaid shaft tothereby impart axial motion to said nut upon rotation of said shaft,said slot having ends against which the nut abuts, and means for movingsaid vnut laterally inthe slot to put a preioad on said balls.

4. In a'manually operated steering gear mechanism of the type utilizinghydraulic power to assist steering, the combination of a motor cylinderwith a piston therein having a slot located intermediate its ends, arotatable shaft in the motor cylinder, bearings in the piston forsupporting said shaft, said piston arranged concentrically on the shaftfor axial movement therealong, fioatable seals located inthe ends of thecylinder and supported on said shaft, said seals being held against theends of the cylinder in a manner to permit limited lateral distortion ofthe shaft caused by eccentricities between said shaft, bearings, andpiston, a nut concentric With the shaft and positioned in said slot forlateral movement relative to said piston, said nut and av portion ofsaid shaft having mating helical grooves therein, a vplurality of ballsin said grooves arranged Vfor `drivably connecting the nuty to saidshaft to thereby impart axial motion to said nut upon rotation of saidshaft, said slotl having ends against which the nut abuts, and means formoving said nut laterally in the slot to put a preload on said balls.

5. In a manually operated steering gear mechanism of the type utilizinghydraulic power to assist steering, the combination of a motor cylinderwith a'piston therein having a slot located intermediate its ends,vafrotatable shaft in the motor cylinder, said piston arrangedconcentrically on the shaft for axial movement therealong, bearings inthe piston for supporting said shaft, a nut concentric with the shaftand positioned in said slot for lateral movement relative to saidpiston, said slot having ends against which the nut abuts, said nut anda portion of said shaft being formed With mating helical groovestherein, a plurality of balls in saidy grooves arranged for drivablyconnecting the nut to said shaft to thereby impart axial motion to saidnut upon rotation of said shaft, a rack carried by said nut, an axiallyshiftable rockshaft in the cylinder, a gear sector arranged in meshingrelationship to said rack and securely mounted on the rockshaft forrotating the same, said gear sector and rack being so formed that axialmovement of said rockshaft will cause lateral displacement of said nut,and means for moving said rockshaft axially.

6. In a manually operated steering gear mechanism of the type utilizinghydraulic power to assist steering, the combination of a motor cylinderwith a piston therein, said piston having axial and lateral openingstherein, a rotatable shaft passing through the axial opening, a nutconcentrieally positioned on the shaft and slidably located in thelateral opening, said lateral 6 opening having'sides forming Aabutmentsfor the nut to thereby restrict its axial movement, mating helicalgrooves in the nut and on a portion of the shaft, and a plurality ofballs in said helical grooves.

STANLEY I. MACDUFF.

REFERENCES CITED y The following references are of record in the le ofthis patent:

UNITED STATES PATENTS n

